Prior art pulse code modulation (PCM) time division multiplexed (TDM) communications typically involve sampling a plurality of channels in a sequence of time and producing a digital word related to the value of the individual channel so sampled. After each of the channels has been sampled, the process is repeated a number of times to produce a PCM frame. Although this is a standard technique of providing PCM/TDM data, the bit stream so organized is difficult to handle for certain applications insofar as the digital samples for the various channels are interleaved. Furthermore, an interruption at a particular point of time in the transmission of the data stream will cause a temporary loss of information in substantially all of the communication channels.
The ground stations of satellite communications systems generally involve a plurality of users attached to the ground station transmitter through common equipment. In prior art systems the plurality of users or "interface modules" were multiplexed and demultiplexed to and from the common equipment generally by employing well-known multiplexers and demultiplexers. The bus structures involved in the multiplexing/demultiplexing operations were configured in a variety of ways such as the radial, party-line (bus), or daisy chain configurations. These prior art techniques are generally large in size and inflexible in nature. That is, the channel allocation for each burst of data for each of the interface modules must be preset by the multiplexer/demultiplexer and changes in channel and/or burst allocation for any one of the interfaced modules requires a substantial reorganization of the multiplex/demultiplex operation.